Bleaching silver images with p-sulfophenyl quinones or p-nitroso phenols



Patented Jan. 13, 1953 BLEACHING SILVER IMAGES WITH p-SULFO- PHENYLQUINONES OR p-NITROSO PI- IE- NOLS George W. Sawdey, Rochester, N. Y.,assignor to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey No Drawing. Application November 1, 1951, Serial No. 254,440

8 Claims. 1

This application relates to color photography and particularly to theremoval of silver images in color photography.

In photographic color processes, such as those in which a colored imageis formed bydevelopment with a primary aromatic amino developing agentin the presence of a coupler compound, the silver images formed in thedevelopment are generally present in the emulsion layer after the dyeimages are formed. These silver images are generally removed byconverting them to a silver salt which is soluble or which is removed byhypo.-' A bath of this type containing potassium ferricyanide andpotassium bromide is disclosed in Mannes, Godowsky, and Wilder U. S.Patent 2,252,718, granted August 19, 1941. A similar bath containing 50grams of potassium ferricyanide and 20 grams of sodium chloride perliter of water to which has been added 1 to 5 grams of potassiumchromate or potassium dichromate to retard the corrosive action of thebath on iron and iron alloys, has also been used.

The ferricyanide and halide bleach baths are not entirely satisfactoryin that certain optical sensitizing dyes in the emulsion layer are notdestroyed by them and these may cause stain in the emulsion layer. Afurther disadvantage is that any ferricyanide remaining in the elementmay be converted to iron oxide and produce a brown stain and there isalso the objectionable corrosive action on stainless steel or ironalloys unless a chromate or dichromate is used in the bath.

A bleach bath containing quinone, acid and an organic solvent has alsobeen used to convert silver images to silver salt in the presence of adeveloped dye image. A bath of this type is disclosed in Mannes andGodowsky U. S. Patent 2,113,329, page 2, column 2, lines 16 to 21. Thisbath cannot be used in the final stages of a color process because itdestroys the dyes as Well as converts the silver to a silver salt.

In addition to the bleaching agents described above, sodium quinonesulfonate has been sugested as a reducer for silver by Lumiere andSeyewetz (British Journal of Photography, 1910, 57 page 625). However,acid solutions of sodium quinone sulfonate lose their bleaching activityrapidly and after about six hours are for all practical purposes uselessas bleaches.

It is, therefore, an object of the present invention to provide novelbleaching agents for bleaching silver images in the presence ofcolor-developed dye images in a photographic emulsion layer. A furtherobject is to provide a novel halogen substituents such as chlorine,bromine or iodine; alkoxy substituents such as methoxy, ethoxy andpropoxy; acetamido groups, etc.

P-sulfophenylquinone ture:

p-Nitrosophenol is commonly regarded as existing in acid solution as themonoxime of benzoquinone according to the scheme The bleaching agents ofmy invention are'usedin strong acid solution, that is, in a solution ofpH from about 1 to about 3.5.

The bleach baths employed according to my invention may be used in anyprocess in.which silver images are present in a photographic layertogether with dye images. The dye images may be those formed by colordevelopment as described in Mannes, Godowsky, and Wilder U. S. Patent2,252,718; Mannes and Godowsky U. S. Patents 2,113,329 and 2,304,940; orJelley and Vittum U. S. Patent 2,322,027. These dyes are of theazomethine, indoaniline or indophenol type. The dyes may also be azodyes such as those used in the silver dye bleach process of colorphotography. After all of the steps of color processing, thephotographic layer or element is treated with the bleach bath of myinvention followed by hypo to remove the silver salts formed by thebleach bath.

The emulsion layers containing the silver and dye images treatedaccording to my invention may be coated on supports of glass or ofcellulose ester, synthetic resin, paper or other suitable material.

has the following struc- The following examples illustrate baths whichmay be used according to my invention.

Water to 500 cc.

The pH of this solution isiapproximately lfii which I have found to beoptimal fo'rthe use-:01

p-sulfophenylquinone, particularly when it is used with emulsions coatedonpaper.

Example :2 Grams-v Cupric chloride 10..

p-Sulfophenylquinone Potassium bromide 5 Sodium bisulfate Water to 500cc.

Both'fof these "bleachibaths eflectfcomplete con version 70f. silver tosilver saltin'acolorrpaper or film in approximately. 10 minutes-.5

Example 3 Grams 1 p Nitrosophenol sodium-salt. 4 Potassium1 bromide-Sodiumhisulfate 15 Tlie-pI-I ofthissolution-isapproximately 1.0. In themajority of-multii-layer color materials, com--- plete'*silverbleaching-is accomplished in- 5 to 10 minutes? The l: le'achbath's of 'my--inventi'on- 'havemany The bleach bath may be fo"r--- or,violently. and therefore good...control. of, the

bleaching actionmay be.obtained,lparticularly at the start of bleaching.

It will Y be understood that the examples included herein areillustrative only and that my inventionis to .be taken as limitedonly bythescope of.theappendednlaims...

I claim:

1..- The. method of v removing, only the silver imagesfrom aphotographic:layer containing. sil.

ver and dye images. which comprises. treating said layer containingsaid; silver and dye images with.

an acid solution of a bleaching agent selected from the class consistingof p-sulfophenylquinone and benzoquinone monoxime and their derivativessubstituted in the aromatic ring with a group selectedirom.the.,classconsisting .of. alkyl, halogen, alkloxy and acetamido -groups,- followedby fixing.

2. The method of removing only the silver images from a photographiclayer containing sil- .vervand color-developed dye images whichoomprises treating'said layer containing said silver and dye images withan acid solution of p-sulfophenylquinone; followed by fixing.

3..The. .'method. ,.of removing only the silver images fromzaphotographic layer containing silver and color-developed dye imageswhich comprisestreating said layer containing said silver and'dye imageswith an acid solution of hemequinonexmonoxime, followed by fixing.

4. The method of removing only the silver images .froma photographiclayer containingsilverand color=developeddye images which com.-v prisestreating said layer containing said silver and dye images with an acidsolution of p-sulfophenylquinone, potassium bromide and sodiumbis'ulfate,.followed by fixing.

5; The method of removing only the silver images from a photographiclayer containing sil-. ver andcolor-developed dye images which comprisestreating said layer containing said silver.

and dye images with an ,acid solution of p nitrosophenol sodium salt,potassium bromide andso? dium bisulfate, followed by fixing.

SJ'AI bleach bath for conversion to silver salt of only. the. silverimages in a photographic layercontaining both silver. anddye images,comprising.

an acid solution of potassium-bromide, sodium bisulfate;and.a bleaching.agent selected from..the class consisting. of p'-sulfophenylquinone,.benz0'-" quinone monoxime and their derivatives substituted inthearomatic. ring with a group selected from the class consisting of alkyl;halogen, alkoxy and acetamido groups.

7. A'ble'ach' bath-"for conversion to silversalt of only the silverimages in a photographic layercontaining both silver and dye images;comprising an acid solution-of potassium bromide, sodium;

bisulfate; and p -sulfophenylquinone.

8. A bleach bathfor conversion to silver salt of only the-silver imagesin a photographic layer containing both silver and dye images;comprising anacid solution of potassium bromide, sodium bisulfate, andbenzoquinonemonoxime sodium salt.

GEORGE W. SAWDEYi No:references;cited.1

1. THE METHOD OF REMOVING ONLY THE SILVER IMAGES FROM A PHOTOGRAPHICLAYER CONTAINING SILVER AND DYE IMAGES, WHICH COMPRISES TREATING SAIDLAYER CONTAINING SAID SILVER AND DYE IMAGES WITH AN ACID SOLUTION OF ABLEACHING AGENT SELECTED FROM THE CLASS CONSISTING OFP-SULFOPHENYLQUINONE AND BENZOQUINONE MONOXIME AND THEIR DERIVATIVESSUBSTITUTED IN THE AROMATIC RING WITH A GROUP SELECTED FROM THE CLASSCONSISTING OF ALKYL, HALOGEN, ALKOXY AND ACETAMIDO GROUPS, FOLLOWED BYFIXING.